Using melt infiltration casting at different temperatures （965, 990 and 1015 °C） for different time （10 and 15 min）, the composites of （Cu50Zr43Al7）99.5Si0.5 bulk metallic glass reinforced with tungsten wir...Using melt infiltration casting at different temperatures （965, 990 and 1015 °C） for different time （10 and 15 min）, the composites of （Cu50Zr43Al7）99.5Si0.5 bulk metallic glass reinforced with tungsten wires were produced. X-ray diffraction （XRD）, scanning electron microscopy （SEM） and quasi-static compression tests were carried out to evaluate the microstructure and mechanical properties. The results show that the maximum ultimate compressive strength and strain-to-failure of about 1880 MPa and 16.7% were achieved, respectively, at the infiltration temperature of 965 °C for 15 min.展开更多
The effects of a pulsed magnetic field on the solidified microstructure of pure Mg were investigated.The results show that microstructure of pure Mg is considerably refined via columnar-to-equiaxed growth under the pu...The effects of a pulsed magnetic field on the solidified microstructure of pure Mg were investigated.The results show that microstructure of pure Mg is considerably refined via columnar-to-equiaxed growth under the pulsed magnetic field and the average grain size is refined to 260？？ under the optimal processing conditions.A mathematical model was built to describe the interaction of the electromagnetic-flow fields during solidification with ANSYS software.The pulsed electric circuit was first solved and then it is substituted into the magnetic field model.The fluid flow model was solved with the acquired electromagnetic force.The effects of pulse voltage frequency on the current wave and on the distribution of magnetic and flow fields were numerically studied.The pulsed magnetic field increases melt convection,which stirs and fractures the dendritic arms into pieces.These broken pieces are transported into the bulk liquid by the liquid flow and act as nuclei to enhance grain refinement.The Joule heat effect produced by the electric current also participates in the microstructural refinement.展开更多
Os isotope ratios of mantle peridotites have been considered to be largely immune to recent melt-rock interaction. However, Os isotope ratios and PGE (Platinum group elements) concentrations of the Yong'an xenolit...Os isotope ratios of mantle peridotites have been considered to be largely immune to recent melt-rock interaction. However, Os isotope ratios and PGE (Platinum group elements) concentrations of the Yong'an xenoliths have been significantly modified by melt percolation, and are not suitable for determining the formation age of lithosphere mantle in Yong'an. In this study, the Yong'an spinel peridotite xenoliths are divided into two groups: N-Type and E-Type. The N-Type group including cpx (clinopyroxene)-poor lherzolite and harzburgite, shows a large variation of Cr#(sp) (13.2-48) and sulfur contents (from 171 ppm to below detection limit), whereas the E-Type peridotites are mainly refractory harzburgites and are characterized by high Cr#(sp) (35.3-42.2) and overall low sulfur contents (below 51 ppm). Both types show similar major and REE (rare earth element) patterns. Furthermore, the N-Type peridotites display a restricted range of iridium-group PGE (IPGE), Os/Ir and Ru/Ir ratios (Os/Ir = 0.64-1.12, Ru/Ir = 1.52-1.79) and variable palladium-group PGE (PPGE) contents (3.4-14.9 ppb), whereas the E-Type peridotites show a large variation of Os/Ir and Ru/Ir ratios (Os/Ir = 0.33-0.84, Ru/Ir = 0.94-1.6), and a restricted range of PPGE (4.3-6.9 ppb). 187Os/188Os ratios of E-Type peridotites are higher than those of N-Type peridotites at comparable fertility levels. These results suggest that N-Type peridotites may have been overprinted by metasomatism via small melt fractions, in which the percolation of the volatile-rich, small melt fractions only resulted in LILE (large ion lithophile element) enrichment of clinopyroxene, and their whole rock PGE contents and Re-Os isotope values were little changed. Moreover, E-Type peridotites may have been modified by melt-rock reaction involving relatively large melt fractions, which may result in the formation of secondary cpx and olivine and the removal of IPGE-bearing minerals such as Ru-Os-(Ir) alloys or laurite, followed by precipitation of secondary sulfides from melt with radiogenic isotopic signature.展开更多
文摘Using melt infiltration casting at different temperatures （965, 990 and 1015 °C） for different time （10 and 15 min）, the composites of （Cu50Zr43Al7）99.5Si0.5 bulk metallic glass reinforced with tungsten wires were produced. X-ray diffraction （XRD）, scanning electron microscopy （SEM） and quasi-static compression tests were carried out to evaluate the microstructure and mechanical properties. The results show that the maximum ultimate compressive strength and strain-to-failure of about 1880 MPa and 16.7% were achieved, respectively, at the infiltration temperature of 965 °C for 15 min.
基金Project(50774075)supported by the National Natural Science Foundation of ChinaProject(2006BAE04B01-4)supported by Key Technologies R&D Program,China
文摘The effects of a pulsed magnetic field on the solidified microstructure of pure Mg were investigated.The results show that microstructure of pure Mg is considerably refined via columnar-to-equiaxed growth under the pulsed magnetic field and the average grain size is refined to 260？？ under the optimal processing conditions.A mathematical model was built to describe the interaction of the electromagnetic-flow fields during solidification with ANSYS software.The pulsed electric circuit was first solved and then it is substituted into the magnetic field model.The fluid flow model was solved with the acquired electromagnetic force.The effects of pulse voltage frequency on the current wave and on the distribution of magnetic and flow fields were numerically studied.The pulsed magnetic field increases melt convection,which stirs and fractures the dendritic arms into pieces.These broken pieces are transported into the bulk liquid by the liquid flow and act as nuclei to enhance grain refinement.The Joule heat effect produced by the electric current also participates in the microstructural refinement.
基金supported by National Natural Science Foundation of China (Grant Nos. 40903019, 40730420, 70914001)project of "CAS Hundred Talents", project of Chinese Academy of Sciences (Grant No.KZCX2-YW-Q04-06)special project of State Key Laboratory of Ore Deposit Geochemistry (Grant No. KCZX20090105)
文摘Os isotope ratios of mantle peridotites have been considered to be largely immune to recent melt-rock interaction. However, Os isotope ratios and PGE (Platinum group elements) concentrations of the Yong'an xenoliths have been significantly modified by melt percolation, and are not suitable for determining the formation age of lithosphere mantle in Yong'an. In this study, the Yong'an spinel peridotite xenoliths are divided into two groups: N-Type and E-Type. The N-Type group including cpx (clinopyroxene)-poor lherzolite and harzburgite, shows a large variation of Cr#(sp) (13.2-48) and sulfur contents (from 171 ppm to below detection limit), whereas the E-Type peridotites are mainly refractory harzburgites and are characterized by high Cr#(sp) (35.3-42.2) and overall low sulfur contents (below 51 ppm). Both types show similar major and REE (rare earth element) patterns. Furthermore, the N-Type peridotites display a restricted range of iridium-group PGE (IPGE), Os/Ir and Ru/Ir ratios (Os/Ir = 0.64-1.12, Ru/Ir = 1.52-1.79) and variable palladium-group PGE (PPGE) contents (3.4-14.9 ppb), whereas the E-Type peridotites show a large variation of Os/Ir and Ru/Ir ratios (Os/Ir = 0.33-0.84, Ru/Ir = 0.94-1.6), and a restricted range of PPGE (4.3-6.9 ppb). 187Os/188Os ratios of E-Type peridotites are higher than those of N-Type peridotites at comparable fertility levels. These results suggest that N-Type peridotites may have been overprinted by metasomatism via small melt fractions, in which the percolation of the volatile-rich, small melt fractions only resulted in LILE (large ion lithophile element) enrichment of clinopyroxene, and their whole rock PGE contents and Re-Os isotope values were little changed. Moreover, E-Type peridotites may have been modified by melt-rock reaction involving relatively large melt fractions, which may result in the formation of secondary cpx and olivine and the removal of IPGE-bearing minerals such as Ru-Os-(Ir) alloys or laurite, followed by precipitation of secondary sulfides from melt with radiogenic isotopic signature.
